A series of Main-chain liquid crystalline polymers with long and
polydisperse soft segments has been synthesized. The thermal properties of
these polymers have been characterized by differential scanning calorimetry,
optical microscopy and wide angle X-ray diffraction. Unexpectedly, these
polymers have a strong tendency to form purely smectic Mesophases. The
degree of ordering of these polymeric mesophases is Much higher than that of
the mesophase formed by a low molecular weight Model compound with the same
Mesogen. The soft segment length effects on thermal behavior of such
segmented copolymers have been elucidated. A semi-quantitative theory has
been formulated to interpret these observations. A phase diagram relating
thermal properties to soft segment length has been proposed.